Sterilizable package

ABSTRACT

There is disclosed a sterilizable container for foodstuffs or the like and comprising a container bowl open at the top and having a circumferential upper edge which is connectable to a lid to form a tight closed unit. The container bowl comprises a cardboard base which is of a particular configuration and provided with crease lines and which is hermetically sealed between two layers of moisture impervious film; the edges of the film extending for a distance beyond the cardboard base so as to provide a portion to which the sealing lid is joined after the base is formed into its finished shape and the container is filled with suitable contents. Also disclosed is a method for fabricating the container, filling it and sealing it.

United States Patent 1191 Christensson [4 1 May 27, 1975 STERILIZABLEPACKAGE [75] Inventor: 0d W. Christensson, Stockholm,

Sweden [22] Filed: Mar. 7, 1974 [21] Appl. No.: 448,941

[52] U.S. Cl 229/43; 229/3.5 MF; 229/14 BL [51] Int. Cl. 865d 5/64 [58]Field of Search 229/3.5 R, 3.5 MP, 14 BL,

10/1968 Buchner et al 229/3.5 MF 1/1969 Christensson 229/43 X PrimaryExaminer-Davis T. Moorhead Attorney, Agent, or Firm-James E. Nilles [57]ABSTRACT There is disclosed a sterilizable container for foodstuffs orthe like and comprising a container bowl open at the top and having acircumferential upper edge which is connectable to a lid to form a tightclosed unit. The container bowl comprises a cardboard base which is of aparticular configuration and provided with crease lines and which ishermetically sealed between two layers of moisture impervious film; theedges of the film extending for a distance beyond the cardboard base soas to provide a portion to which the sealing lid is joined after thebase is formed into its finished shape and the container is filled withsuitable contents. Also disclosed is a method for fabricating thecontainer, filling it and sealing it.

9 Claims, 8 Drawing Figures SHEET PAIEM 13 :rmmm

STERILIZABLE PACKAGE The present invention refers to a sterilizablecontainer especially intended for food-stuffs and comprising a containerbowl open at the top. which bowl is made of a liquid-tight material andwhich along the upper edge thereof is connected to a lid to form atight, closed unit.

'he invention is more particularly directed to such a container which ismade of a base of cardboard or similar stiff material and a liquid andgas-tight lining of a thin and easily formable material. The inventionalso refers to a method of manufacturing such containers.

Containers of the above mentioned kind are previously known which aremade of a container blank of cardboard or similar stiff materialcomprising a number of wall panels and bottom closure flaps and topclosure flaps which are integral with the said wallpanels and whichtogether form the bottom and the top, respectively. of the finishedcontainer. Generally, a lining of plastic or similar thin and easilyformable tight material is attached to one or two of the walls of theouter container. whereupon the container is folded together, erected andclosed at the bottom.

Such containers are disadvantageous in several respects. Due to theseveral joints both in the lining and the outer container extendingalong the side panels and the bottom and top of the container. it isdifficult to get such a container completely tight. Further, since thelining is resting loosely against the outer container at least along twosides and the bottom and top, and since the lining under normalconditions cannot completely fill the interior of the outer container,the lining with its contents may move during transportation or handlingof the container, and this sometimes leads to a rupture of the liningdue to friction damage, whereby the lining begins to leak. Since,further, the lining can normally not be made to penetrate closely intothe corners of the outer container. there will be some stretching in thelining when closing the bottom and top of the container, and the saidstretching causes a thinning of the lining at such spots and there willbe an increased risk of penetration of the lining with subsequentleakage.

In order to provide a container which is as tight as possible, it hasbeen proposed that the container should he formed as an integral flatcontainer blank having a central bottom and side pieces, corner panelsand corner fold pieces integral with the said central bottom withoutbeing parted therefrom and a lining which is attached at points at leastto the bottom. When raising the side pieces and the corner panels andfolding in the corner fold pieces a completely tight container bowlwithout joints is obtained which may later be provided with a sealinglid. Also, with such prior art containers there is. however, a risk thatthe lining moves during transportation or handling which may causerupture of the lining and subsequent leakagev Since, further, the outercontainer is made of cardboard, such a container is not very suited forsterilizing which is usually accomplished by means of super-heatedsteam. since the hygroscopic cardboard material will then absorb liquidand be damaged Consequently. containers of this kind have not previouslybeen used for packing such products which ought to be sterilized.Instead, in such cases. containers or packages of thin stiff plasticmaterial have usually been used. The latter packages are essentiallymore expen- The present invention, therefore, concerns the problem ofproviding a lined cardboard container which is suited for packingofproducts which are to be sterilized and which container may bemanufactured quickly and simply at a comparatively low cost by means ofconventional machines.

The solution of this problem is, according to the invention. to providea container blank comprising at least two liquid tight layers ofa thinand easily formable material which between themselves enclose astabilizing cardboard material, whereby the cardboard material and thetwo cover materials or foils are connected to form a solid unit, and inaddition thereto the solution of the problem is that the combinedcontainer unit is formed as an unbroken unit including bottom and sidepieces, corner panels and corner fold pieces which are integral with thebottom and which when raised form a completely tight container bowl, andfurther that the stabilizing cardboard material leaves a border freeround the upper edge of the container, so that the said border part iscomposed only by the thin foils which may easily be connected to a lidpiece so as to form a tight and closed container.

Further characteristics of the invention will be evident from thefollowing detailed description in which reference will be made to theaccompanying drawings.

In the drawings FIG. 1 shows a plain blank for a container according tothe invention.

FIG. 2 shows in a perspective view a raised container bowl made of theblank shown in FIG. 1.

FIG. 3 shows the container bowl of FIG. 2 from above.

FIG. 4 is a partial cross-section view of the container of FIG. 3 seenalong line IV-IV.

FIG. 5 is a partial cross-section showing the structure of a containerside and the lid associated therewith.

FIG. 6 is a diagrammatical showing of an apparatus for manufacturingblanks for the container.

FIGS. 7 and 8 are cross-sectional views showing alternative embodimentsof the container according to FIGS. 1-4.

The container shown in the drawings generally comprises a container bowlI, a lid seal foil 2 and an upper edge strengthening means 3. Thecontainer bowl may further be provided with a re-closable lid, whichdoes not however form a part of the invention.

The container bowl is made of a plain blank without joints, and theblank is made of at least two thin and easily formable foils whichbetween themselves hermetically enclose a stiffening means of cardboard.As is best evident from FIG. 5, a stiffening means 5 is thus enclosedbetween an outer foil 6 and an inner foil 7, which foils may be of thesame or different kinds and consist of a thin and easily formablematerial like a plastic material. It is required that the said foilsmust be completely free of smell and taste so that the package can beused for food stuffs, aromatic compounds and the like, and in additionit is required that the said foils can stand the high temperatures atwhich the finished container is to be sterilized without being subjectedto mechanical or chemical transformation. Normally the sterilizingprocess takes place at about 121C, which means that the foils must beheat resistant up to at least 130C. For this purpose it has been foundsuitable to use ethylene materials which are heat resistant up to atleast 130C or polypropylene materials which are heat resistant up to atleast 150C. Other plastic materials may also be used.

There are very strong requirements of tightness in a container forsterilized products and, in order to prevent osmosis or other activitywhich may occur through the plastic material, a foil of an inert metallike an aluminum foil 8 is interposed between the cardboard stiffeningmeans 5 and the inner plastic foil 7. Usually the inner foil 7 and thealuminum foil 8 are supplied as a combined laminate and are therebyconsidered and treated as one unit.

In FIG. 1 there is shown one embodiment of a blank for a container bowlwhich is formed as an integral unit and comprises a bottom 9 and fourbowl sides 10 integral therewith, four corner panels 11 and, between thecorner panels 11 and the bowl sides 10, corner fold pieces 12. The bowlsides 10 and the corner panels 11 are delimited from the bowl bottom 9by creasing lines 13, and the corner panels 11 are in the same waydelimited from the bowl sides 10 by creasing lines 14. At the bottom ofthe container the corner panels 11 form an angle of 45 with respect tothe adjacent bottom sides but in order to provide a rounded form of thecorner panels 11 at the upper edge of the container, the said panels areformed with several parallel creasing lines 15 which make it possible toobtain a round form as shown for instance in FIGS. 2 and 3. The outerform of the blank for the container bowl is such that the bowl in theerected state provides an even upper edge.

The cardboard material is substantially thicker than the foil 6, 7 and 8and in order to avoid stretching in the foils or any creap leakageswhich may arise when a thick material is bent in sharp folds, thecardboard stiffening means 5 is smaller than the outer foil 6, the innerfoil 7 and the aluminum foil 8, and is placed centrally between the saidfoils. In an erected container there is formed a thin upper edge 16around the container, which edge is only composed of the three foils 6,7 and 8. The total thickness of the said three foils is so small thatthe unit may be bent with sharp folds without the risk that creapleakages will arise at the said folds. Contributing to this is the factthat all the foils are easily bendable and have essentially betterelasticity than is the case with the cardboard stiffening means 5.

The forming of the creasing in the blank to form the container bowl maytake place only by shaping the cardboard stiffening means before this isjoined in between the foils 6, 7 and 8, but the actual folding suitablytakes place after the joining of the cardboard stiffening means betweensaid foils.

Since the container is to be subjected to temperatures of about 120C, itis of importance that the cardboard stiffening means 5 contain verylittle air and a very little amount of water, since otherwise air orsteam bubbles may arise between the cardboard stiffening means and thefoil. Usually the cardboard material has an amount of moisture of 5060%,but for present purposes the amount of moisture should be as low as 4%.If considered necessary, the cardboard material may therefore besubjected to a drying process and perhaps also a pressing operationbefore being enclosed between the foils 6, 7 and 8.

The erection of the container bowl is accomplished by bending the bowlsides 10 upwards from the level of the bowl bottom 9 and at the sametime folding the corner fold pieces 12 inwards and attaching the same tothe inside of the adjacent bowl side 10. This is most clearly shown inFIG. 3. The attaching of the corner fold pieces 12 preferably is done bywelding, whereby the plastic material of the corner fold pieces 12 meltstogether with the plastic material of the bowl sides 10. At the sametime or immediately following the attaching of the corner fold pieces,the corresponding parts are welded together along the upper edge 16 andby this welding operation a completely tight joint is obtained betweenthe corner fold pieces 12 and the bowl sides 10. At the same time,equalizing is obtained of the little difference in thickness which ispresent due to the, triple foil composition which is present at thecorners.

The enclosing of the cardboard stiffening means between the foils may beaccomplished by glueing or welding in a lamination operation and it isthereby of importance that an intimate contact is obtained between thefoils and cardboard stiffening means. Such an intimate contact assuresthat the inner foil which corresponds to the lining of a conventionalcontainer completely follows the cardboard stiffening means as far asinto the corners, and thereby the risk of stretching and any ruptures ofthe foil in connection with the formation of the bowl is eliminated.

After the container bowl 1 has been erected as described above, it isfilled with the product, whereupon the bowl is sealed with a lid sealfoil 2 of a known type, which fo'il is welded against the inside of theupper edge 16 of the container bowl. The lid seal foil 2 suitably is alaminate of an aluminum foil and a plastic foil of the same type as thelaminate 7, 8 at the inside of the container bowl. In order to increasethe stability of the upper edge 16 formed by the foils 6, 7 and 8 andthe lid seal foil 2, this edge 16 may be provided with an edgestrengthening means 17 consisting of a frame having a groove which isopen in the downward direction and in which the projecting edge 16 ofthe container bowl may be secured by glueing, welding or the like.Thanks to the lamination of the cardboard stiffening means 15 with theouter foil 6 and the inner foil 7 and aluminum foil 8, it is possible tocompletely utilize the stiffness of the said foils and it is possible tosubstantially reduce the thickness of the cardboard material comparedwith what has previously been possible. A container of this kind may,therefore, be made thin and light-weight but in spite of this verystable.

In an alternative embodiment of the invention the cardboard stiffeningmeans 5 may be substituted for by a basket 18 or the like made of aplastic material which provides the necessary stiffening of the foilmaterial, and the said basket may, as shown in FIG. 7, be applied withinthe bowl consisting only of a foil material or having a cardboardstiffening means or, as shown in FIG. 8, be applied outside thecontainer bowl prior to or after the filling and the sealing thereof.

The container according to the invention is manufactured in thefollowing way. A blank for a container bowl is manufactured asdiagrammatically shown in FIG. 6. From a pile 19 of cardboard stiffenersthe cardboard stiffeners 5 are successively fed between a web of outerfoil 6 on one side and a web of aluminum foil 8 and an inner foil 7 onthe other side. Before this, if considered necessary, the amount ofmoisture in the cardboard material is reduced in a drying operation.After the cardboard stiffeners 5 have been fed between the foil webs,they are preferably pressed between hot rollers whereby a welding takesplace of the foils along the edge 16 so that the cardboard material ishermetically enclosed between the said foils. Not until this is done arethe different blanks cut to separate container bowl blanks which arepresented to a station at which they are creased and erected, at whichthe corner fold pieces 12 are secured, the upper edge is welded and thebowl is filled and sealed by means of the lid seal foil as describedabove. In this condition the filled and sealed container is sterilizedby being subjected to a suitable sterilization temperature which in aparticular case was 121C. Such sterilizing generally takes place bymeans of super-heated steam in a steam autoclave, and it is importantfor this purpose that the foils 6, 7 and 8 completely preventpenetration of moisture to the hygroscopic cardboard material 5, sincethe package would otherwise be ruined by swelling of the cardboardmaterial. It is important that the cardboard material have theabove-mentioned low moisture and air content so that no steam or airbubbles penetrate between the cardboard material and the foils. In orderto effectively prevent such penetration it may be suitable to separatelyweld the upper edge 16 of the bowl after the cardboard material has beenlaminated with the foil.

After the steam sterilization the container may be provided with an edgestrengthening means 17 and a re-closable lid 4.

The above described container in accordance with the invention may inmany cases replace conventional preserve-tins, may be manufactured at alower cost and in a simpler manner by means of available machines, andmay, therefore, form a complement for other packing methods forsterilized products. The container may also be given any suitable formand may be made pliable. The finished laminated blanks for the containerbowls, which may be supplied to the place of filling and sealing thecontainer, take up very little space thanks to their flat or plane form.It is to be understood that the above specification is only of anexemplifying nature and that all kinds of modifications may be presentedwithin the scope of the appended claims.

I claim:

1. A sterilizable container comprising a container bowl of aliquid-tight material which bowl is open at the top and which isconnected along the upper edge thereof to a lid thereby forming a tight,closed unit, characterized in that said container bowl is formed by atleast two thin foils which are intimately contacting a base of a stiffmaterial disposed therebetween wherein said base extends a distance lessthan the distance to said upper edge of said container bowl, and whereinsaid foils are joined together along said upper edge and said lid isjoined in sealed relationship with the non-strengthened upper part ofsaid container bowl.

2. Container according to claim 1 wherin said base is hermeticallyenclosed between said two foils and the non-strengthened upper part ofsaid container bowl is composed only by said foils welded togetherthereby forming a connected unit.

3. Container according to claim 2 wherein said base is laminatedtogether with said foils thereby forming an integral unit with saidfoils.

4. Container according to claim 1 wherein said base is a basket which isplaced within said container bowl which comprises said foils.

5. Container according to claim 1 wherein said base is a basket which isplaced outside said container bowl which comprises said foils.

6. Container according to claim 1 wherein said container bowl is formedby a flat uninterrupted blank including a bottom and container sideswhich are integral with the said bottom and with corner panels andcorner fold pieces to provide a container bowl without any joints.

7. Container according to claim 2 wherein the inner foil of said twofoils is a laminate comprising an outer aluminum foil and an inner foilof a plastic material which is resistant to sterilizing temperatures.

8. Container according to claim 1 wherein said lid comprises a lid sealfoil in the form of a laminate comprising an inner plastic foil and anouter aluminum foil, said lid seal foil being connected to and weldedagainst the inside of said non-strengthened upper edge part of saidcontainer bowl.

9. Container according to claim 1 wherein said nonstrengthened upperedge part of said container bowl is enclosed in a frame of a stiffmaterial.

l I l

1. A sterilizable container comprising a container bowl of aliquid-tight material which bowl is open at the top and which isconnected along the upper edge thereof to a lid thereby forming a tight,closed unit, characterized in that said container bowl is formed by atleast two thin foils which are intimately contacting a base of a stiffmaterial disposed therebetween wherein said base extends a distance lessthan the distance to said upper edge of said container bowl, and whereinsaid foils are joined together along said upper edge and said lid isjoined in sealed relationship with the non-strengthened upper part ofsaid container bowl.
 2. Container according to claim 1 wherin said baseis hermetically enclosed between said two foils and the non-strengthenedupper part of said container bowl is composed only by said foils weldedtogether thereby forming a connected unit.
 3. Container according toclaim 2 wherein said base is laminated together with said foils therebyforming an integral unit with said foils.
 4. Container according toclaim 1 wherein said base is a basket which is placed within saidcontainer bowl which comprises said foils.
 5. Container according toclaim 1 wherein said base is a basket which is placed outside saidcontainer bowl which comprises said foils.
 6. Container according toclaim 1 wherein said container bowl is formed by a flat uninterruptedblank including a bottom and container sides which are integral with thesaid bottom and with corner panels and corner fold pieces to provide acontainer bowl without any joints.
 7. Container according to claim 2wherein the inner foil of said two foils is a laminate comprising anouter aluminum foil and an inner foil of a plastic material which isresistant to sterilizing temperatures.
 8. Container according to claim 1wherein said lid comprises a lid seal foil in the form of a laminatecomprising an inner plastic foil and an outer aluminum foil, said lidseal foil being connected to and welded against the inside of saidnon-strengthened upper edge part of said container bowl.
 9. Containeraccording to claim 1 wherein said non-strengthened upper edge part ofsaid container bowl is enclosed in a frame of a stiff material.